A federal jury in the United States has indicted the former chairmen of the world's two largest auction houses, Sotheby's and Christies, on charges of overcharging its customers.

The US Justice Department said the charges - against Alfred Taubman and Anthony Tennant, respectively former chairmen at Sotheby's and Christies - related to commission rates charged to sellers in the US and elsewhere between 1993 and 1999.

It said sellers in the US alone were charged more than $400m in commissions during the six years of the alleged conspiracy.

I look forward to the opportunity to clear my name in court

Alfred Taubman, former chairman of Sotheby's

If convicted, the men face each a maximum sentence of three years in prison and a $350,000 fine.

Christies and Sotheby's are reported to control more than 90% of the world's live auctions of art, jewellery and furniture.

The indictments come seven months after Sothebys and its former chief executive, Diana Brooks, known as Dede, pleaded guilty to price-fixing, earning the company a $45m fine.

Mr Taubman, an American citizen, issued a statement saying: "I am absolutely innocent ... whatever Dede Brooks chose to do, she did on her own and without my authorisation.

"While any trial is difficult, I look forward to the opportunity to clear my name in court," he said, adding that he had passed a lie-detector test.

There has been no comment from Mr Tennant, who is British, or Christies.

Christies is reported to have been co-operating with the Justice Department under a "leniency" programme which ensures it avoids prosecution if it voluntarily reports involvement in a crime.

In December 2001, Sotheby's former chairman Alfred Taubman was tried in New York and found guilty of conspiring to fix commissions charged to clients. Four months later, he was sentenced to one year in prison.

Anthony Tennant, his co-accused and opposite number at Christies, refused to leave Britain and could not be extradited because there was no equivalent criminal offence in the UK.

Much of the case against Mr Taubman, a self-made billionaire, rested on the testimony of his former chief executive Diana "Dede" Brooks. She said that for much of the 1990s the chairmen of the two apparently rival auction houses had a secret deal to fix commissions.

The scam, which scandalised the art world, is estimated to have overcharged Sotheby's sellers more than $40 million.